pub fn odd_fibnacci_sum(threshold: u32) -> u32 {
  let mut sum = 0;

  let mut fb_1 = 0;
  let mut fb_2 = 1;

  while fb_2 <= threshold {
    if fb_2 % 2 !=0 {
      sum += fb_2;
    }
    [fb_1, fb_2] = [fb_2, fb_1 + fb_2];
  }
  sum
}
